Many industries have a need for materials that can increase the viscosity of aqueous-based compositions such as aqueous solutions or dispersions or emulsions having an aqueous continuous phase. In many instances, a particular viscosity is desired or necessary for ease in handling, dispensing, or otherwise using a product. Coating compositions, such as latex paints, must have sufficient viscosity to avoid excessive dripping from the applicator. Personal care products, which are often applied by hand, generally must have sufficient viscosity to cling to the hand of the user, and then to the hair, or skin, or other point of application. For instance, if a hand lotion had a fluidity approaching that of water, until completely dried a significant portion would be transferred to and deposited on anything the user may touch. A watery hair-set lotion would run through the user's fingers and off the hair during application. To such type of formulations a separate ingredient or ingredients are often added to increase viscosity to the desired level. Such materials are called thickeners or thickening agents.
It is desirable that such thickening agents provide the desired viscosity at a low add-on level to minimize cost. It is desirable that such agents be compatible with other ingredients in the formulation at use level. Thus the nature of a given thickener must be taken into consideration together with that of the other components of the composition. Moreover, desired activity of the thickener at low use levels may diminish potential incompatibilities. It is also desirable to have available a group of thickening agents from which to select one to provide a particular viscosity level at a particular add-on level.
In the personal care product industry thickening agents based on anionic polymers are widely known, such as carboxy vinyl polymers.
There are sufficient compatibility problems between such anionic polymers and other formulation components that effective alternatives are being sought.